This application is the national phase under 35 U.S.C. xc2xa7 371 of PCT International Application No. PCT/DE00/00182 which has an International filing date of Jan. 9, 2000, which designated the United States of America and which is hereby incorporated herein by reference.
The invention relates to a method for producing a module of a current path of a switching device, the module comprising a rigid contact body and a flexible conductor piece including component conductors.
Modules of this type are a component part of much electrical switchgear, in particular that in which the rigid contact body is movably arranged and can be actuated by a drive mechanism for switching the switching device on and off. For this purpose, the rigid contact body, provided with a contact facing, interacts with a relatively fixed mating contact. A relatively fixed arrangement is understood in the present context as meaning that a component referred to in this way is a component part of a switching device which includes the movable contact arrangement.
The previously known methods of the type stated at the beginning are based on the idea that a rigid contact body produced from a solid material is provided, for example by punching out from copper sheet, and that a section of the semifinished product in the form of a cable or strand is securely connected to this contact body by welding or soldering. Since the quality of the connection between the flexible conductor piece and the rigid contact body is decisive for the switchgear to have an adequate service life, only methods which provide a not only mechanically durable but also equally electrically high-grade connection come into consideration for the connection of the parts. A contact arrangement and a method for connecting a contact body to a flexible conductor are described for example in EP 0 467 798 A1 or DE 44 16 104 A1.
The switchgear considered here includes multipole low-voltage power circuit breakers with a nominal current of up to several 1000 A, which have a plurality or a multiplicity of contact bodies for each pole. In the case of such power circuit breakers, the costs for the connection of the contact bodies to the flexible conductors represent a not inconsiderable part of the overall production costs.
FR 1 279 798 A discloses a method which serves for connecting a wire to a rigid conductor. According to this method, a part-length of the wire is compressed into a dovetail-shaped groove of a connection piece or some other conductor piece by applying a pressure. In this case, the cross section of the wire is chosen such that it is only partly accommodated in the groove and a remaining residual volume forms a cross-sectionally mushroom-like or web-like protrusion. In the compressing operation, the wire becomes plastic, whereas the connection piece or conductor piece with the groove is deformed only elastically. Therefore, an unreleasable connection, required for the purposes of the invention, between the two conductors to be connected is not obtained.
On the basis of a method of the type explained at the beginning, the invention is based on the object of permitting inexpensive production of modules of the type mentioned with good quality.
This object is achieved according to the invention by a part-length of a section of a semifinished product, forming the flexible conductor piece, being subjected to mechanical compression by means of a pressing force up to the flow limit and the rigid contact body being completely or partially formed as a result, while the flexible conductor piece is formed by a second part-length of the section of said semifinished product, not subjected to the compression.
In the method according to the invention, neither is a solder material supplied nor is a high temperature used. Consequently, the difficulties frequently occurring previously, such as rupture of the flexible conductor piece at the point of connection with the rigid contact body or an increased transition resistance, are avoided in principle.
Within the scope of the invention, a first part-length of a section of a semifinished product used for producing the flexible conductor piece may be brought into contact with a bearing face, intended for the connection, of a separately provided contact body and said part-length may be mechanically compressed by a pressing force acting against the bearing face to produce a laminar connection.
According to another embodiment of the invention, the rigid contact body may be produced by mechanical compression of a first part-length of a section of a semifinished product used for producing the flexible conductor piece, while the flexible conductor piece is formed by a second part-length of the section of said semifinished product which is not subjected to the compression. The advantage of this method is that only the semifinished product which is used for the production of the flexible conductor pieces is required for producing the module comprising the contact body and flexible conductor.
A further advantageous refinement of the above methods allows the integration of the modules considered here into a switching device to be made easier. For this purpose, mechanical compression of a third part-length of the section of the semifinished product is used for forming a connection piece serving for connection to a relatively fixed conductor of the switching device.
If the semifinished product used within the scope of the invention, for example fine-wired copper strand, is of a clean and uniform quality customary for electrotechnical purposes, it will be possible when an appropriate pressure is applied to produce compressed articles with a density which is not inferior to customary solid material. However, it is not possible to rule out the possibility of the semifinished product used being locally soiled and or partially oxidized during storage or already during production. If such a material is processed as part of an automated production process, parts deviating from the prescribed quality standard may be formed, without this being externally evident. The cause may be, for example, inclusions and inadequate binding. According to one refinement of the methods described, quality deviations of the type described can be avoided by the mechanical compression being carried out in the presence of a flux. A further advantage which is achieved is that a lower pressure is adequate and, as a result, the material and compression mold undergo less severe loading.
If use is made of the possibility of producing the module by using an existing contact body, this can preferably take place by using a compression mold which has a chamber for receiving an end part of the contact body and the first part-length of the semifinished product and also has an entry opening for the part-length of the semifinished product, the pressing force being exerted by means of an associated press die.
If, on the other hand, it is envisaged to produce the contact body in the way mentioned completely from the semifinished product for flexible conductor pieces, the method can advantageously take place by using a compression mold with a chamber which corresponds to the contact body and has an entry opening for the first part-length of the section of the semifinished product. The pressing force is likewise exerted by means of an associated press die.
Both aforementioned types of method can also be used for producing a contact arrangement with two or more flexible conductor pieces for each contact body. For this purpose, a compression mold with an entry opening dimensioned to correspond to the complete cross section of the conductor pieces can be used.
It has already been mentioned that the rigid contact bodies are provided with a contact facing dimensioned in a way corresponding to the respectively given switching task. According to a further refinement of the method described, such a contact facing may be embedded at least partly into the semifinished product during the compression of the semifinished product. To facilitate this embedding, the contact facing may be provided with at least one continuation intended for the embedding into the semifinished product.
The invention is explained in more detail below on the basis of the exemplary embodiments represented in the figures.